1. Field of the Invention
The present invention relates to an organic light emitting device (OLED) in which paracyclophane or a paracyclophane derivative is used as the emissive layer and/or one or more of the charge transport layers, or as a host material for one or more of such layers.
2. Description of the Related Art
Significant efforts have been expended in developing suitable materials for use in organic light emitting devices (OLEDs). Such devices are commercially attractive because they offer the promise of low-cost fabrication of high-density pixeled displays exhibiting bright electroluminescence with long life times and wide color range.
A typical OLED is fabricated by sandwiching an emissive layer between an anode and a cathode. When a bias is applied across the electrodes, holes and electrons are respectively injected from the anode and cathode into the emissive layer, typically facilitated by hole transport and electron, transport layers adjacent to the respective electrodes. The holes and electrons radiatively combine in the emissive layer and emit light. Improved performance can be obtained if blocking layers are provided to block against the injection of either holes or electrons from the adjoining layer and their subsequent escape from the device. Some of these layers can be combined. For example, a double-layered structure is fabricated from a combined hole-injecting and transporting layer together with a combined electron-transporting and light-emitting layer. Likewise, a triple-layered structure is composed of a hole-injecting and transporting layer, a light-emitting layer, and an electron-injecting and transporting layer.
In addition, it is possible to form these layers from a host material doped with another material designed to achieve the desired effect of the layer (for example, to achieve a hole transport effect, an electron transport effect, or an emissive effect).
Because of consumer expectations of good efficiency, long lifetime and pure color, a need exists for development of suitable materials for the various layers.